Fuel injection nozzle

Abstract: A two stage lift fuel injection nozzle includes a nozzle holder (10) in which is defined a chamber (16) housing a pair of springs (15, 24) disposed in axial relationship. The springs provide a two stage biasing force for a valve member (13) slidable in a nozzle body (11) which is secured to one end of the holder. The spring (24) which is adjacent the nozzle body engages a reaction member (26) in the form of an annular component (30) defining legs (31) which can be expanded outwardly into gripping engagement with the wall of the chamber by means of a plug (32) which is in screw thread engagement with the component.

Description: This invention relates to fuel injection nozzles of the kind comprising a nozzle holder to one end of which is secured a nozzle body containing a fuel pressure actuated valve member which controls the flow of fuel through an outlet, a chamber defined in the holder and a pair of springs located in axial relationship within the chamber and operable to provide a two stage biasing force on the valve member, the one of said springs remote from the nozzle body engaging a reaction surface disposed at the end of the chamber remote from the nozzle body and the other of the springs engaging a reaction element located intermediate the ends of the chamber. The aforesaid reaction element could be in the form of a step in the wall of the chamber but this would result in the nozzle holder having an increased diameter as a result of the provision of the step. It is known from GB-A-2251891 to form the reaction element as an annular member which is secured in position in the chamber after the one of the springs has been assembled into the chamber. The method of securing the annular member is to deform the wall of the chamber by pressure applied to the exterior surface of the nozzle holder. This method of retention requires the appropriate material to be used in the manufacture of the nozzle holder and this material may not be ideal to withstand the stresses to which the holder is subjected in use. Moreover, once the reaction element has been secured it is no longer possible to gain access to the one spring for the purpose of adjustment. SU-A-947461 describes an arrangement in which a reaction element is secured in position by means of a screw threaded member which is in screw threaded engagement with the housing of an injector. The screw threaded member engages the reaction element at a position spaced from the axis of the rotation element. The object of the present invention is to provide a fuel injection nozzle of the kind specified in a simple and improved form. According to the present invention there is provided a fuel injection nozzle comprising a nozzle holder to one end of which is secured a nozzle body containing a fuel pressure actuated valve member which controls the flow of fuel through an outlet, a chamber defined in the holder and a pair of springs located in axial relationship within the chamber, the springs providing a two stage biasing force for the valve member, the one of the springs remote from the nozzle body engaging a reaction surface disposed at the end of the chamber remote from the nozzle body, and the other of the springs engaging a reaction element located intermediate the ends of the chamber characterised in that said reaction element comprises an annular component which can be inserted into the chamber to the desired position, said annular component defining a plurality of axially extending, angularly spaced legs, and a plug which can be screw threadedly engaged with the component to urge the legs outwardly into gripping engagement with the interior wall of the chamber. An example of a fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawings in which:- Figure 1 is a sectional side elevation of the nozzle, Figure 2 is a view to an enlarged scale of portion of the nozzle seen in Figure 1, Figure 3 is a plan view of the portion of the nozzle seen in Figure 2, Figure 4 is an underside view of the portion of the nozzle seen in Figure 2, and Figures 5 and 6 are views similar to Figures 2 and 3 showing a modification. Referring to Figure 1 of the drawings the nozzle comprises a generally cylindrical nozzle holder 10 to one end of which is secured a nozzle body 11 using a conventional cap nut 12. The nozzle body contains a fluid pressure actuated valve member 13 which controls the flow of fuel through an outlet orifice 14 formed in an extended portion of the nozzle body. Within the nozzle body there is defined a seating and the valve member 13 is biased into engagement with the seating by a first coiled compression spring 15 which is housed within a cylindrical chamber 16 formed in the nozzle holder 10 and extending inwardly from the end thereof engaged with the nozzle body. The chamber 16 communicates with a drain outlet 17 formed in the holder and also formed in the holder is a fuel inlet 18 which is connected by means of a passage 19 extending within the holder to a further passage 20 formed in the nozzle body, the passage 20 communicating with a gallery through which the valve member extends. The spring 15 has one end engaged with a spring abutment 21 and its other end is engaged with the end wall of the chamber through the intermediary of a shim 22. The force exerted by the spring 15 is transmitted to the valve member 13 by way of the spring abutment 21 and then by means of a push rod 23 which is engaged with a reduced end portion of the valve member 13 which projects from the nozzle body 11. Surrounding the push rod is a further spring 24 one end of which is engaged with an abutment plate 25. The other end of the spring is engaged with a reaction element 26 to be described. The abutment plate 25 is of generally triangular shape and it is urged by the spring 24 into engagement with the end face of the nozzle body 11. A small clearance exists between the plate and a step defined on the valve member and a further small clearance exists between the plate and three stop surfaces 27 which are defined adjacent the entrance to the chamber. In operation, when fuel under pressure is supplied through the inlet 18 the fuel pressure acts upon the valve member to generate an axial force which is opposed by the spring 15. When the pressure rises to a sufficiently high value the force exerted by the spring 15 is overcome and the valve member lifts until the aforesaid step on the valve member engages with the abutment plate 25. The limited lift of the valve member allows fuel to flow through the outlet orifice 14 at a restricted rate. As the fuel pressure increases the valve member moves further but in this case it is against the action of both springs and the maximum extent of movement of the valve member is limited by the abutment of the plate 25 with the stop surfaces 27. The initial force exerted on the valve member by the spring 15 is determined by selection of the shim 22 and once the shim is selected the reaction element 26 is placed in position and locked against axial movement. The force exerted by the spring 24 is adjusted again by the use of a shim which is interposed between the reaction element and the end of the spring remote from the abutment plate. Figure 2 shows to an enlarged scale, the construction of the reaction element and with reference to Figures 2, 3 and 4 the reaction element comprises an annular component 30 from which extends a plurality of axially extending and angularly spaced legs 31 the outer surfaces of which are provided with grooves. At their outer ends the inner surfaces of the legs are tapered outwardly and the radially inward surfaces of the legs are provided with thread formations. The reaction element also includes a plug 32 having a central bore of non-circular section which is large enough to allow the passage therethrough of the push rod 23. The plug 32 is also provided with a tapered portion for engagement with the tapered surfaces of the legs 31. When assembling the reaction element the plug is loosely engaged with the threaded portions of the legs and then pushed into position in the chamber. By use of a tool which is located in a slot 33 formed in the end surface of the component 30, the latter can be restrained from rotation and by use of an appropriately shaped driver engaged within the non-circular bore in the plug, the plug 32 can be rotated to urge the legs 31 outwardly into firm engagement with the wall of the chamber. Should it be necessary to remove the component this can be readily effected by unscrewing the plug and withdrawing the reaction element. In a modification, the tapered portions on the legs and plug are omitted and the plug and legs are formed with a tapered screw thread which as the plug is rotated relative to the component forces the legs outwardly. In the arrangement shown in Figures 5 and 6, the plug 35 is engaged within the component 36 from the opposite end so that the direction of the tapered portions on the plug and the legs 37 is reversed. Moreover, the curved surfaces of the legs 37 which engage with the wall of the chamber lie in their free state, on a circle which is slightly larger than the diameter of the chamber 16 so that when the component 36 is pushed into position the legs are deformed inwardly by a small amount so that a light force is required to move the reaction member into position. Once the desired position is reached the plug is rotated relative to the component to urge the legs outwardly into firm engagement with the wall of the chamber. In this example the initial frictional engagement between the legs 37 and the wall of the chamber should be sufficient to restrain the component against rotation. However, if desired a slot similar to the slot 33 may be provided. As with the previous example by providing tapered threads, on the legs and the plug it is possible to eliminate the aforesaid tapered portions.

Claims: A fuel injection nozzle comprising a nozzle holder (10) to one end of which is secured a nozzle body (11) containing a fuel pressure actuated valve member (13) which controls the flow of fuel through an outlet (14), a chamber (16) defined in the holder and a pair of springs (15, 24) located in axial relationship within the chamber, the springs providing a two stage biasing force for the valve member (13), the one of the springs remote from the nozzle body (11) engaging a reaction surface disposed at the end of the chamber remote from the nozzle body, and the other of the springs engaging a reaction element (26) located intermediate the ends of the chamber (16) whereby said reaction element comprises an annular component (30, 36) which can be inserted into the chamber to the desired position, characterised in that said annular component defines a plurality of axially extending, angularly spaced legs (31, 37), and comprises a plug (32, 35) which can be screw threadedly engaged with the component to urge the legs (31, 37) outwardly into gripping engagement with the interior wall of the chamber. A nozzle according to Claim 1, characterised in that said plug (32, 35) is provided with a through bore to allow a push rod (23) to pass therethrough, said push rod acting to transmit the force exerted by said one spring. A nozzle according to Claim 2, characterised in that said through bore is of non-circular section. A nozzle according to Claim 1, characterised in that said plug (32, 35) and said legs (31, 37) are provided with cooperating tapered surfaces which co-act to urge the legs outwardly as the plug is tightened. A nozzle according to Claim 1, characterised in that the plug and component are provided with tapered screw threads.

Inventors: STEVENS JOHN WILLIAM, STEVENS, JOHN WILLIAM
Applicants: LUCAS IND PLC, LUCAS INDUSTRIES PUBLIC LIMITED COMPANY
Application year: 1994
Main classification: F02M45
IPC codes: F02M61, F02M45